chiadoan.cpp

#include <bits/stdc++.h>
using namespace std;

#define ll long long

int main() {
    freopen("in", "r", stdin);
    ll l, n;
    cin >> l >> n;
    priority_queue<ll, vector<ll>, greater<ll> > pq;
    for (int i = 0; i < n; i++) {
        ll x; cin >> x;
        pq.push(x);
        l -= x;
    }
    if (l != 0) pq.push(l);
    ll ans = 0;
    while (pq.size() > 1) {
        ll a = pq.top(); pq.pop();
        ll b = pq.top(); pq.pop();
        ll s = a + b;
        ans += s;
        pq.push(s);
    }
    cout << ans << '\n';
}